Wireless communication systems are widely used to provide a voice service or a packet service. A multiple access system supports communication to multiple users by sharing available system resources. Examples of the multiple access system include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, etc.
3-rd generation partnership project (3GPP) long term evolution (LTE) is an evolution of a universal mobile telecommunication system (UMTS) and is introduced in the 3GPP release 8. The 3GPP LTE uses OFDMA in a downlink, and uses single carrier-FDMA (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having 4 antennas. 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE has recently been discussed.
Automatic repeat request (ARQ) is an error control mechanism which uses acknowledgment to achieve reliable data transmission. The acknowledgment is a status report message transmitted by a receiver to a transmitter to indicate whether the receiver has successfully received data.
If the ARQ is performed in a radio link control (RLC) layer, hybrid automatic repeat request (HARQ) is performed in a medium access control (MAC) layer that is a lower layer of the RLC layer. The HARQ is a combination of the ARQ and forward error correction (FEC) coding that is an error correction mechanism, and an HARQ acknowledgement (ACK)/negative-acknowledgment (NACK) signal is exchanged in a physical layer. If the received data is successfully decoded, the HARQ ACK/NACK signal is an HARQ ACK signal, and if the received data is unsuccessfully decoded, the HARQ ACK/NACK signal is an HARQ NACK signal.
In the HARQ, the HARQ ACK/NACK signal is periodically/aperiodically transmitted for each HARQ process. On the other hand, in the ARQ, to reduce an overhead caused by a status report, the receiver reports the status report in general when the transmitter requests the status report (this is referred to as polling).
In principle, the ARQ and the HARQ are performed independently from each other. However, since the RLC layer performs the ARQ by receiving a data block from the MAC layer in which the HARQ is performed, an operation error of one layer may affect to the other layer.
The RLC layer may receive a duplicated data block from the MAC layer. For example, an HARQ ACK-to-NACK error may occur when the receiver feeds back an HARQ ACK signal to the transmitter upon receiving an initial data block but the transmitter mistakenly recognizes the HARQ ACK signal as an HARQ NACK signal by being affected by a wireless channel and thus retransmits the same data block as the initial data block. A MAC layer of the receiver may transmit a data block which is duplicated to the initial data block to an RLC layer of the receiver. In this case, if the duplicated data block is a polling data block, that is, a data block for requesting a status report, the RLC layer may duplicatively transmit the status report. This may result in an overhead caused by the redundant status report. In addition, unnecessary retransmission may occur when the receiver reports the status report at a time not desired by the transmitter during the ARQ is performed.
Accordingly, there is a need for a method capable of handling a status report request for a duplicatively received data block.